Open and read closed workbook

I have a workbook and I need to loop all rows in a closed workbook.
What is the correct way to write the macro?

I have a UserForm where I select the workbook, so I know the path to it.
It is the first sheet I need to read. (unknown sheetname, not Sheet1)
And the columns I have to read is A and B until the first empty row.

Links for tutorials for this, or anything else would help me since I'm new to VBA.

Thanks for any help with this.

Does the workbook need to stay closed or can you open it, read what you want into your current workbook and then close the one you are reading out of.
If it is OK to open then close the workbook then I would suggest recording a macro and doing this to get you started.

You can then add a For - Next loop or a Do Loop to get the information you want transfered to your workbook.

I would prefer to loop a closed workbook without opening it, but I do not know how.
But maybe that is impossible?